It is known that many materials exhibit superconducting properties when they are cooled below "the critical transition temperature". Materials have been discovered recently that exhibit superconducting properties at increasingly higher critical transition temperatures. One family of materials that exhibit this type of superconducting property are the perovskites. Included in this family are compositions in the Ba-La-Cu-O, the La-Sr-Cu-O, and the Y-Ba-Cu-O systems. In particular, compositions in the Y-Ba-Cu-O system have been observed to have a superconducting transition temperature as high as 90.degree. K.
The as made Y-Ba-Cu-O perovskite has a oxygen deficiency and or a tetragonal crystal structure and does not exhibit superconductivity at as high a transition temperature. It is only when this material is further oxidized and changes phase to an orthorhombic crystal structure that the high critical transition temperature (90 K) is exhibited.
In order to reach the required oxidation state for such high temperature superconductivity, they are conventionally annealed by cycling its temperature to above 550.degree. C. These high processing temperatures have frustrated attempts to develop practical applications of these superconducting materials because such temperatures are incompatible for maintaining the minimum feature sizes of the range of semiconductor electronic devices required to implement superconductor devices. This incompatibility at such processing temperatures is caused by interdiffusion or alloying of the various materials used to fabricate both semiconducting and superconducting microelectronic devices. Additionally, the high processing temperatures constrain the application of conventional microlithographic techniques, such as photoresist patterning of such electronic circuits and magnetic structures.
In one attempt to reduce the high temperatures necessary to oxidize the perovskite materials to obtain high temperature superconducting properties plasma oxidation in a cylindrical reactor was tried. This was reported in an article entitled "Plasma Oxidation Of High T.sub.c Superconducting Perovskites" by Bagley et.al., published in Applied Physics Letters on Aug. 24, 1987. Therein, Bagley et.al. discloses the use of a cylindrical reactor having a power density of less than 0.005 W/cm.sup.3 with an oxygen pressure of 0.7 Torr operating at a frequency of 13.56 MHz. The heating of the sample was constrained to less than 80.degree. C. but the required exposure to obtain a reasonable degree of superconductivity in the sample was in excess of several hundred hours. The application of direct and capacitively coupled plasma reactors in oxidizing the potentially high temperature superconducting materials has not achieved the desired result of permitting their practical applications. Therefore, there exists a need to advance even further in bringing these potentially tremendously beneficial materials to practical and commercial applications.